Printing plate, printing machine, printing method, and apparatus for manufacturing liquid crystal device, and method for manufacturing the same

ABSTRACT

A printing plate ( 1 ) includes, on the printing surface of a raised part ( 2 ), grooves ( 3 ) passing through from one side to another thereof. Preferably, the grooves ( 3 ) are parallel to each other and equally spaced apart. More preferably the raised part ( 2 ) is in the shape of a nearly-rectangular frame, and the grooves ( 3 ) are provided such that one side of the near-rectangle and the longitudinal direction of the grooves ( 3 ) form an angle of 45°.

TECHNICAL FIELD

The present invention relates to a printing plate and a press, and moreparticularly to a flexographic plate and a method for flexography thatallows printing substance with a more thickness to be transferred to aprinting substrate. The present invention further relates to anapparatus and method for manufacturing liquid crystal devices, and moreparticularly to an apparatus and method for printing sealing materialthat bonds the panel substrates together.

BACKGROUND ART

Flexography is a type of relief printing that uses a flexographic plateof flexible rubber or resin, and a liquid printing substance. Currently,printing substrates (which is understood as any object on which printingis performed) that can be used for printing with this method includepaper as well as cellophane and aluminum foil, and the like.

FIG. 10 illustrates a printing unit that constitutes a key component ofa flexographic press. The printing unit includes an impression table 11that supports a printing substrate 10, a printing plate 1 having araised part 2, a plate cylinder 12, an anilox roll 16, a dispenser 18,and a doctor roll 15. Printing substance 17 such as ink is supplied toanilox roll 16 using dispenser 18. Anilox roll 16 and plate cylinder 12are in the shape of cylindrical rolls that contact each other and arerotated in the directions indicated by arrows 48 and 46, respectively.Plate cylinder 12 includes on its perimeter surface printing plate 1that has raised part 2 in a configuration that corresponds to the designto be printed. Raised part 2 and printing substrate 10 are disposed tobe in contact with each other. Printing substance 17 is applied toraised part 2 by anilox roll 16 and then transferred to printingsubstrate 10. Printing substrate 10 is disposed on a main surface ofimpression table 11 and is moved in the direction indicated by arrow 47as printing proceeds. The transferred design is defined by the topsurface configuration of raised part 2. The substance that has beenprinted onto printing substrate 10 and has the configuration of raisedpart 2 is hereinafter referred to as a “printed substance”. In thepresent example, the printed substance 4 is in the shape of a frame.

The curved perimeter surface of anilox roll 16 is contacted by raisedpart 2 as well as doctor roll 15. Doctor roll 15 serves to uniformlyspread printing substance 17 supplied by dispenser 18 over the perimetersurface of anilox roll 16. Thus, doctor roll 15 is disposed in contactwith anilox roll 16 between the location where printing substance 17 issupplied and the location where it is in contact with raised part 2.

Alternatively, a plate-like doctor blade may be used that replaces, andfunctions similarly to, doctor roll 15. Further, a flexographic pressmay include a cylindrical fountain roll that replaces, and functionssimilarly to, dispenser 18 to supply printing substance 17 to aniloxroll 16.

Conventionally, flexography has been used for printing characters andgraphics onto packaging papers. However, as it may be employed informing thin films, it is also used for other purposes than printingcharacters and graphics. For example, flexography may be used forforming alignment layers for a liquid crystal display, with a glassbeing the printing substrate and a polyimide thin film being printed onits surface.

Flat panel displays using e.g. a liquid crystal panel are employed in avariety of devices such as mobile phones, personal digital assistants,televisions and the like. The liquid crystal panel thereof has liquidcrystal that is sealed between a pair of panel substrates spaced apartat a predetermined distance. A thermosetting or UV curing seal is usedto bond the liquid crystal panels together along their periphery and toprevent the liquid crystal from leaking.

In recent years, a method of manufacturing liquid crystal panels calledthe dropping and panel-alignment method, or the dropping and fillingmethod, has gained in popularity. The method preforms a frame-shapedseal on one of a pair of panel substrates and then drops a predeterminedamount of liquid crystal within the frame. The panel substrate is thenbonded together with the other panel substrate under a depressedatmosphere before retrieving them to the ambient atmosphere to produce aliquid crystal panel. The method allows the filling of liquid crystaland the bonding together of the two panel substrates simultaneouslywithout leaving bubbles in the liquid crystal.

Conventional methods of forming a seal for the liquid crystal panelinclude the screen-printing method, the dispensing method and the like.In the screen printing, a screen mesh comes in contact with the surfaceof a printing substrate including a panel substrate and may scratch analignment layer on the panel substrate, resulting in a decreaseddisplaying quality. To prevent this, as disclosed in Japanese PatentLaying-Open No. 9-258194, methods have been proposed to separate thescreen mesh from the printing substrate by inserting a spacertherebetween. This, however, requires emulsion to be thinly spread onthe alignment layer, which may easily be punctuated, often causing thesealing material to be printed on the alignment layer. The dispensingmethod (see Japanese Patent Laying-Open No. 5-15818) uses a dispensingnozzle to print unicursally a frame using sealing material for eachcell, which takes a long time. For example, it is inefficient whenprinting hundreds of small frames of sealing material on one panelsubstrate.

Consequently, methods have been developed for forming a seal withoutscratching the surface of the printing substrate while using flexographywith improved productivity.

For a small film thickness of a seal in the dropping and panel-alignmentmethod, when two opposed panel substrates are bonded together, part ofthe liquid may leak through a gap between the seal and the panelsubstrate prior to the entire periphery of the seal being in contactwith the panel substrate to seal the liquid therein. Air may also enterthe liquid crystal panel through a gap between the seal and the panelsubstrate upon retrieving the panel substrates from the depressedatmosphere to the ambient atmosphere. Accordingly, the pre-printed sealshould have a thickness equal to or greater than 20 μm, and preferably athickness in the range from 25 to 30 μms.

Flexography is suitable for producing a thin film of 0.01-1 μm. For afilm thickness greater than several micrometers, attempts have been madeto increase the amount of substance transferred from the anilox roll tothe raised part of the printing plate by providing dot-like dimples onthe raised part of the printing plate, as disclosed in Japanese PatentLaying-Open No. 10-217418. However, conventional flexography can stablyproduce a film thickness of around 10 μm, at most. The thickness ofprinting substance transferred to the printing substrate is hereinafterreferred to as the “film thickness”. Trying to produce a greater filmthickness requires correspondingly larger dot-like dimples on the raisedpart of the flexographic printing plate. However, printing substance isoften insufficiently supplied from the anilox roll into the dot-likedimples, which leaves bubbles, resulting in bubbles in the printedsubstance after printing or in printed lines being partially narrower (anarrower portion of the printed line is hereinafter referred to as the“narrowness”).

The present invention solves the above-mentioned problems. An object ofthe present invention is to provide a relief printing plate and methodof printing using the same, and an apparatus and method formanufacturing liquid crystal devices that allow printing for producing afilm thickness greater than would be achieved by the conventional artwithout causing bubbles or narrownesses.

DISCLOSURE OF THE INVENTION

A printing plate according to the present invention includes a raisedpart for transferring printing substance to a printing substrate and, ona printing surface of the raised part, a groove passing through from oneside to another thereof. In other words, a relief printing plate has, ona printing surface of a raised part in the design to be printed, agroove passing through from one side to another thereof. By employingthis configuration, the raised part only needs to have a groove on itsprinting surface to transfer, onto the printing substrate, more printingsubstance held on the printing plate than would be the case using theconventional art. Thus, printing can be performed to produce a filmthickness greater than using the conventional art. The “printingsurface” means a surface of the raised part that holds printingsubstance and provides the transfer by contacting the printingsubstrate.

Preferably, in the invention stated above, the groove has a crosssection generally in the shape of a triangle. In other words, the grooveis not in the shape of, for example, a box, but is in a V-shape on theprinting surface of the raised part. This configuration may facilitatethe formation of the groove when using a printing plate made of e.g.photo-curing resin.

Preferably, in the invention stated above, grooves extend in onedirection parallel to each other and equally spaced apart. Thisconfiguration can minimize non-uniformity of printing substance placedonto the printing substrate, thereby enabling the printing substance tobe transferred with an even thickness.

Preferably, in the invention stated above, the printing plate is for aflexographic press and the groove has a width, along the printingsurface of the raised part, of not less than 20 μm and not more than 60μm, a depth of not less than 25 μm and not more than 75 μm, and adistance between the grooves of not less than 20 μm and not more than 60μm. More preferably, the printing plate includes a raised part in theshape of a nearly-rectangular frame where a side of the near-rectangleis parallel to the longitudinal direction of the groove and the raisedpart is arranged such that the nearly-rectangle has a side in a slantingdirection relative to the moving direction of the printing plate. Thisconfiguration can reduce the occurrence of bubbles and narrownesses inthe printed substance when the printing substance is a sealing materialfor a display panel, thereby providing printing for producing a filmthickness greater than would be achieved using the conventional art.Alternatively, the printing plate may include a raised part in the shapeof a nearly-rectangular frame where a side of the near-rectangle formsan angle of approximately 45° with the longitudinal direction of thegroove. More preferably, the moving direction of the printing plate isgenerally perpendicular to the longitudinal direction of the groove. Themoving direction of the printing plate may also be generally parallel tothe longitudinal direction of the groove. This configuration may furtherdecrease bubbles and narrownesses in the printed substance mentionedabove when the printing substance is a sealing material for a displaypanel.

A press according to the present invention includes a printing plate asdescribed above. A press with a printed plate as described above canminimize the occurrence of bubbles and narrownesses and perform printingto produce a film thickness greater than would be achieved using theconventional art.

An apparatus for manufacturing a liquid crystal device according to thepresent invention includes a printing plate as described above. Thisconfiguration can minimize the occurrence of bubbles and narrownesses inthe printed substance. Thus, two panel substrates may be bonded togetherwhile preventing liquid crystal from leaking out or preventing air frombeing trapped.

A printing method according to the present invention involves a reliefprinting including the step of printing by pressing a printing platehaving a raised part onto a printing substrate, the raised part having,on a surface for transferring printing substance, a plurality of groovespassing through from one side to another thereof, and the step ofdisposing the printing plate on the perimeter surface of a cylindricalplate cylinder and transferring the substance to the printing substrateby rotating the plate cylinder. The step of transferring is performedusing a flexographic press. By employing this method, flexography canform printed substance with a film thickness greater than would beachieved using the conventional art.

Preferably, in the invention stated above, the raised part is in theshape of a nearly-rectangular frame, the grooves are linear onesparallel to each other and equally spaced apart, and the printingsubstance to be printed onto the printing substrate is a sealingmaterial. By employing this method, flexography can print onto theprinting substrate a sealing material with a thickness greater thanwould be the case using the conventional art.

Preferably, in the invention stated above, the sealing material is onefor a flat panel display, and the grooves have a width along the surfaceof the raised part of not less than 20 μm and not more than 60 μm, adepth of not less than 25 μm and not more than 75 μm, and a distancebetween the grooves of not less than 20 μm and not more than 60 μm .This method can minimize the occurrence of bubbles and narrownesses inthe printed substance, with a film thickness greater than by theconventional art.

Preferably, in the invention stated above, the step of transferringincludes the step of rotating the plate cylinder while using a printingplate having grooves being parallel to one side of the near-rectangle,where the moving direction of the printing plate forms an angle ofapproximately 45° with the longitudinal direction of the grooves.Alternatively, the step of transferring includes the step of rotatingthe plate cylinder while using a printing plate that includes groovesforming an angle of approximately 45° with one side of thenear-rectangle, with the moving direction of the printing plate beinggenerally perpendicular to the longitudinal direction of the grooves.Alternatively, the step of transferring includes the step of rotatingthe plate cylinder while using a printing plate that includes groovesforming an angle of approximately 45° with one side of thenear-rectangle, with the moving direction of the printing plate beingparallel to the longitudinal direction of the grooves. This method canfurther minimize the occurrence of bubbles or narrownesses in theprinted substance.

A method of manufacturing a liquid crystal device according to thepresent invention includes the printing method described above. Theprinting method described above may be employed in a method formanufacturing liquid crystal devices to provide printing for producing afilm thickness greater than would be achieved using the conventionalart, while preventing sealed liquid crystal from leaking out orpreventing air from being trapped in the liquid crystal when the twopanel substrates are bonded together.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a plan view of a printing plate of a first embodimentaccording to the present invention.

FIG. 1B is a cross sectional view in the direction of the arrow of IB-IBin FIG. 1A.

FIG. 2A is a plan view of a printing plate of a second embodimentaccording to the present invention.

FIG. 2B is a cross sectional view in the direction of the arrow ofIIB-IIB in FIG. 2A.

FIG. 3 is a plan view of a printing plate used for a first printingtest, shown together with the moving direction.

FIG. 4 is a perspective view of a printing unit of a flexographic pressused for first and second printing tests.

FIG. 5 is a plan view of a printing plate used for a second printingtest, shown together with the moving direction.

FIG. 6 illustrates a correlation between the printing plate and themoving direction in the second printing test in the first embodiment ofthe present invention.

FIGS. 7A and 7B illustrate correlations between the printing plate andthe moving direction in the second printing test in the secondembodiment of the present invention.

FIGS. 8A and 8B illustrate one printing plate provided for comparison.

FIGS. 9A and 9B illustrate another printing plate provided forcomparison.

FIG. 10 is a perspective view of a printing unit of a flexographic pressaccording to the conventional art.

FIG. 11 is a plan view of a printing substrate illustrating defectsoccurring while printing substance is printed onto a printing substrate.

BEST MODES FOR CARRYING OUT THE INVENTION

(First Embodiment)

Referring to FIGS. 1A and 1B, a printing plate of a first embodimentaccording the present invention will be described. FIG. 1A is a planview showing a raised part of a printing plate, while FIG. 1B is a crosssectional view in the direction of the arrow of IB-IB in FIG. 1A.

Raised part 2 on a main surface of printing plate 1 is in the shape of anearly-rectangular frame with arc corners. Raised part 2 has atrapezoidal cross section with the shorter one of its bases representingthe printing surface. The printing surface i.e. the top of raised part 2has a plurality of linear grooves 3 parallel to one side of thenear-rectangle. In the present embodiment, one side of thenear-rectangle parallel to grooves 3 has three grooves 3. All of grooves3 pass from one side to another of raised part 2. The grooves areparallel to each other and spaced apart at a certain distance. One sideof the near-rectangle is parallel to one of the edges of printing plate1. Grooves of the kind shown in FIG. 1A are hereinafter referred to as“parallel grooves”. In the present embodiment, the parallel grooves holdprinting substance to provide an increased thickness of the printedsubstance.

In the present embodiment, raised part 2 is made of photo-curing resin.Providing the photo-curing resin with a mask and then illuminating itwith ultraviolet light causes the illuminated region thereof to becured, where a portion thereof that is shadowed by the mask remainsuncured and is subsequently removed to form a groove. In the presentmethod, the region thereof that is shaded by the mask is triangular.This can be utilized to facilitate the formation of grooves with atriangular cross section, which is the case with the cross section ofthe grooves of the present embodiment. Alternatively, the shape of thecross section may be a trapezoid or the like and is not limited to atriangle.

The inventors have conducted numerous printing tests to identify thefunction and effect of the printing plate according to the presentinvention. Two such tests are illustrated, which are referred to as thefirst and second printing tests. The first printing test compares theperformances of different configurations of the raised part of theprinting plate, created by the inventors. For comparison with theprinting plates according to the present invention, a printing plate wasselected having a raised part with lattice-shaped grooves and one havinga raised part with a wide groove. The results of the first printing testwill be described using the two printing plates selected and theprinting plate according to the present embodiment.

(First Printing Test)

Configurations of raised part 2 of the printing plate for comparisonused in the first printing test are shown in FIGS. 8A and 8B and FIGS.9A and 9B. FIGS. 8A and 8B show a raised part with lattice-shapedgrooves 3. FIG. 8A is a plan view of printing plate 1, while FIG. 8B isa cross sectional view in the direction of the arrow of VIIIB-VIIIB inFIG. 8A. Grooves 3 have a triangular cross section and are parallel toeach other. The grooves in this configuration will be referred to as“intersecting grooves”. The intersecting grooves are provided over theentire printing surface of raised part 2. FIGS. 9A and 9B show a groove3 having a relatively large width, which will be referred to as a “widegroove”. FIG. 9A is a plan view of raised part 2. The wide groove isframe-shaped and parallel to the contour of raised part 2. FIG. 9B is across sectional view in the direction of the arrow of IXB-IXB in FIG.9A. The printing surface of raised part 2 has one wide groove 3 whichhas a trapezoidal cross section. The shorter one of the bases of thetrapezoid provides the bottom surface of groove 3.

The first printing test arranges a plurality of raised parts regularlyon a rectangular printing plate 1 as shown in FIG. 3, where each of thesides of a nearly-rectangular raised part is parallel to thecorresponding one of the sides of printing plate 1. For each of theconfigurations of the grooves, four types of raised parts were providedhaving different dimensions of the raised parts and grooves to conductthe first printing test. Raised parts 13 a-13 d have different groovedimensions and different outer dimensions. To illustrate theconfigurations of the raised parts and grooves, raised parts havingdifferent printing surface widths 5, and different groove distances 6,groove widths 7 and groove depths 8 were formed, which are labeled asTest Nos. <1>-<4>. As the test number increases from <1>to <4>, largergrooves are provided in the raised part to produce increased filmthickness of the printed substance.

In the present embodiment, printing surface width 5, i.e. the width ofthe printing surface of the raised part, ranges from 300 to 360 μm, thedistance 6 between the grooves that defines the pitch for the groovesfrom 50 to 20 μm, groove width 7 from 20 to 80 μm, and groove depth 8,i.e. the depth of each groove, from 25 to 100 μm.

In FIG. 3, raised parts 13 a-13 d have configurations of Test Nos.<1>-<4>, respectively. To eliminate the dependence of the test resultson the location of a raised part within printing plate 1, thearrangement of Test Nos. <1>-<4> is altered from column to column.Printing is performed in the direction indicated by moving direction 40.

As shown in FIG. 4, printing plate 1 is attached onto the perimetersurface of plate cylinder 12. In the first printing test, plate cylinder12 is rotated in the direction of arrow 46, and printing substrate 10,together with impression table 11, is moved in the direction of arrow47, as in the conventional art. Impression table 11 is moved with thedirection of its advancement being parallel to the longitudinaldirection of printing plate 1 to perform printing on printing substrate10. The first printing test used a plate cylinder 12 with a radius of127 mm and operated it with a print speed of 1.0 m/min. as measured bythe peripheral speed of plate cylinder 12, where the printing materialwas a UV curing sealing material with a viscosity of 350 Pa·s.

To evaluate of the results, the thickness and appearance of the printedsubstance i.e. printing substance printed onto a printing substrate wereobserved to determine its quality. The appearance was observed by visualinspection or microscopy. The criterion for the evaluation was whetheror not the printed substance included bubbles or narrownesses. FIG. 11shows examples of bubbles 27 and a narrowness 25. FIG. 11 illustratesdefects of the printed substance transferred to printing substrate 10when printing was performed in the moving direction 40.

The results from the first printing test are shown in Table 1 below.Table 1 also includes the results from a first printing test with theoblique grooves in a second embodiment, which will be described belowwith reference to the second embodiment. TABLE 1 Results from FirstPrinting Test [μm] Dimension Results from Printing Test Groove TestPrinting Surface Groove Groove Groove Film Line Bubble/ Type No. WidthDistance Width Depth Thickness Width Narrowness Parallel <1> 300 50 2025 14˜17 330˜350 ◯ <2> 300 45 40 50 26˜28 340˜365 ◯ <3> 300 20 60 7530˜33 355˜370 ◯ <4> 360 20 80 100 33˜39 440˜460 X Oblique <1> 300 60 2025 13˜16 325˜345 ◯ <2> 300 45 40 50 25˜27 330˜355 ◯ <3> 300 20 60 7530˜34 340˜360 ◯ <4> 360 20 80 100 32˜37 425˜450 X Intersecting <1> 30060 20 25  7˜10 315˜330 ◯ <2> 300 45 40 50 15˜17 320˜340 X <3> 300 20 6075 17˜25 320˜350 X <4> 360 20 80 100 19˜30 405˜430 X Wide <1> 300 60 18020 12˜14 330˜360 ◯ <2> 300 60 180 30 15˜20 335˜365 X <3> 300 60 180 4020˜26 345˜380 X <4> 360 60 240 40 21˜27 415˜450 X◯: No bubble or narrownessX: Bubble or narrowness present

The results from the first printing test show that the use of a printingplate with the intersecting grooves, a groove configuration that wasprovided for comparison, allowed printing without bubbles ornarrownesses when a film thickness to be produced was between 7 to 10 μmas in Test No. <1>. Similarly, the use of a printing plate with the widegroove allowed printing without bubbles or narrownesses for a filmthickness ranging from 12 to 14 μm as in Test No. <1>. In Test Nos.<2>-<4> of each groove, where the grooves had larger cross sections toproduce greater film thicknesses, the film thicknesses were actuallyincreased for these types of grooves but bubbles 27 or narrownesses 25were observed in printed substance 4.

On the contrary, the first printing test for the parallel grooves, i.e.using a printing plate according to the present embodiment, resulted ina good printed substance 4 without bubbles 24 or narrownesses 25 with afilm thickness of up to 30-33 μm as in Test No. <3>.

Based on the foregoing, a preferable mechanism in the raised part forfixing transferred substance includes grooves passing through from oneside to another of the raised part. Preferably, all the grooves areparallel to each other and equally spaced apart.

The results of the first printing test were provided by using a UVcuring sealing material for flat panel displays having a viscosity of350 Pa·s, although similar effects were observed when a UV curingsealing material having a viscosity ranging from 250 to 500 Pa·s wasused.

The first printing test was conducted with a constant moving directionand with varying configurations of the grooves. More specifically,printing was performed such that the direction in which the raised partcame in contact with the printing substrate was parallel with the longerones of the sides of the nearly-rectangular raised part. As shown in theresults from the first printing test, the use of a printing plate havinga raised part with the parallel grooves provided a printed substancewith increased film thickness and with a higher precision in size.However, increasing the print speed to improve productivity sometimescaused narrownesses or bubbles even with a printing plate with theparallel grooves and, in addition, produced a ball-shaped portion of theprinted substance in some locations (the ball-shaped portion ishereinafter referred to as a “ball”). FIG. 11 illustrates exemplaryballs 26. A ball 26 is produced when printing substance 17 sticks toprinting plate 1, which may cause the substance to be extended like along thread. Balls 26 were produced particularly in those of the sidesof raised part 2 that have grooves 3 with a relatively small length.

(Second Printing Test)

The quality of the printed substance is affected by the angle formed bythe longitudinal direction of groove 3 and the moving direction. Theeffect of this angle on the quality of the printed substance wasconsidered in a second printing test. The consideration was made bycomparing the printed substance that was printed with a groove 3 in aslanting direction relative to, i.e. not parallel to, the movingdirection, and the printed substance that was printed with a groove 3parallel to the moving direction, where their respective print speedswere altered to compare the performance for the moving directions. Inthe present example, the longitudinal direction of groove 3 deviatedfrom the moving direction at an angle of 4520 .

FIGS. 5 and 6 are plan views of a printing plate 1 illustrating themethod of the second printing test. As shown in FIG. 5, it is similar tothe first printing test in that the raised parts with parallel groovesare disposed regularly on a main surface of printing plate 1, and thearrangement of raised parts 13 a-13 d is also similar to that of thefirst test. Comparison was made referring only to the printing plateswith raised parts corresponding to Test No. <2> in Table 1. The secondprinting test also provided that grooved printing plate 1 was turned by45° counterclockwise when being brought into contact with the printingsubstrate. Moving direction 40 in FIGS. 5 and 6 is the direction inwhich the plate on the plate cylinder is rotated i.e. in which theprinting is performed. As shown in FIG. 6, the longitudinal direction ofthe parallel grooves forms an angle of 4520 with the moving direction.This condition was maintained while the print speed was altered toperform the printing test. The results of the second test are shown inTable 2.

Table 2 also includes the results of a printing test with the obliquegrooves in the second embodiment, which will be described referring tothe second embodiment. TABLE 2 Results from Second Printing Test TestResults Print Speed Groove Turning 0.7 1.0 1.4 2.0 Type Angle Typem/min. m/min. m/min. m/min. Parallel  0° ball ◯ ◯ X X <2> bubble/ ◯ ◯ XX narrowness 45° ball ◯ ◯ ◯ X Counter bubble/ ◯ ◯ ◯ X clockwisenarrowness Oblique  0° ball ◯ ◯ X X <2> bubble/ ◯ ◯ ◯ X narrowness 45°ball ◯ ◯ ◯ ◯ Counter bubble/ ◯ ◯ ◯ X clockwise narrowness 45° ball ◯ ◯ ◯◯ Clockwise bubble/ ◯ ◯ ◯ ◯ narrowness◯: No ball, or no bubble or narrownessX: Ball present, or bubble or narrowness present

In Table 2, the column “Turning Angle” indicates angles formed by alonger side of the nearly-rectangular raised part and the movingdirection, and the direction of turn. 0° indicates that the direction ofa longer side of the near-rectangle is the same as the moving direction.The results were evaluated considering the occurrence of bubbles ornarrownesses as in the first printing test as well as the occurrence ofballs. The test was conducted with different print speeds for 0° and for45° counterclockwise. For 0°, it is similar to the printing method inthe first printing test, where only the print speed is changed. For 45°counterclockwise, the printing was performed in the moving direction 40,as shown in FIG. 6. The print speed is measured on the perimeter surfaceof plate cylinder 12 i.e. the speed with which the printing substrate ismoved during printing. For 0°, the printed substance had no balls,bubbles or narrownesses at a print speed of not more than 1.0 m/min. Atthe print speed of 1.4 m/min., both balls and bubbles or narrownesseswere produced.

On the contrary, the printing with printing plate 1 turned by 45°counterclockwise resulted in a printed substance without balls, bubblesor narrownesses at a print speed of not more than 1.4 m/min. When thespeed was increased to 2.0/min., balls, bubbles or narrowness wereproduced.

Thus, when using parallel grooves, the printing may be conducted with aslanting direction of movement relative to the longitudinal direction ofthe grooves to increase the print speed while maintaining high qualityof the printed substance, contributing to the improvement inproductivity. Although the present embodiment illustrates the printingwith the direction of the parallel grooves forming an angle of 45° withthe moving direction, it is not limited to this angle.

(Second Embodiment)

Referring to FIGS. 2A and 2B, a printing plate of a second embodimentaccording to the present invention will be described. FIG. 2A is a planview showing a raised part of a printing plate, while FIG. 2B is a viewof the printing plate in the direction of the arrow of IIB-IIB in FIG.2A.

Again, in the present embodiment, the shape of the raised part on theprinting plate is a nearly-rectangular frame. In the first embodiment,grooves 3 are parallel to a side of the near-rectangle. The presentembodiment is different from the first embodiment in that thelongitudinal direction of grooves 3 are in a slanting direction, i.e.,neither parallel nor perpendicular to a side of the near-rectangle. Suchgrooves are hereinafter referred to as “oblique grooves”. In the presentembodiment, the grooves shown in FIG. 1A are turned counterclockwise by45° to provide the grooves shown in FIG. 2A.

In the cross section along the line IIB-IIB, three grooves 3 areprovided. Grooves 3 are parallel to each other. Similar to the firstembodiment, the grooves pass through from one side to another of theraised part.

(First Printing Test)

Table 1 provided above shows the results of a first printing testconducted in a similar manner to that of the first embodiment.

In the present embodiment, printing surface width 5 i.e. the width ofthe printing surface of a raised part ranges from 300 to 360 μm,distance 6 between the grooves which determines the pitch for thegrooves from 60 to 20 μm, groove width 7 from 20 to 80 μm, and groovedepth 8 i.e. the depth of a groove from 25 to 100 μm.

Of Test Nos. <1>-<4>, Test No. <4> with largest grooves exhibitedincreased film thickness but caused bubbles or narrownesses in theprinted substance as well, while grooves that produce film thicknessesof up to 30 -34 μm as in Test No. <3> provided a good printed substancewith a greater film thickness and without bubbles or narrownesses. Thisis an improvement over the intersecting and wide grooves, similar to thefirst embodiment. For example, comparison is made among the test resultsfrom the four groove configurations in terms of Test No. <2>. Theparallel and oblique grooves provide printing without bubbles ornarrownesses, while the intersecting and wide grooves cause bubbles ornarrownesses.

The results of the first printing test were provided by using a UVcuring sealing material for flat panel displays with a viscosity of 350Pa·s, as in the first embodiment. However, using a UV curing sealingmaterial with a viscosity ranging from 250 to 500 Pa·s exhibited similareffects.

Both the first printing test for the first embodiment and the firstprinting test for the second embodiment produced good results for thegroove configurations of Test Nos. <1>-<3>. Consequently, grooves of thetwo types are preferred to have the configurations of Test Nos. <1>-<3>.In other words, the grooves in the raised part preferably have a widthalong the printing surface of a raised part, with which the printingsubstrate comes in contact, of not less than 20 μm and not more than 60μm, a depth of not less than 25 μm and not more than 75 μm, and adistance between the grooves of not less than 20 μm and not more than 60μm . These groove configurations are particularly useful when sealingmaterial for flat panel displays using e.g. liquid crystal is selectedas the printing substance, and a panel substrate for liquid crystalpanels as the printing substrate.

(Second Printing Test)

A second printing test was conducted in a similar manner to that of thefirst embodiment. In the first embodiment, it is obvious that the testresults are the same for a clockwise turn by 45° and for acounterclockwise turn by 45°. In the present embodiment, however, theangle formed by the moving direction and the longitudinal direction ofthe grooves differs depending upon the direction of turn, and thus thesecond printing test was conducted for both the clockwise turn by 45°and the counterclockwise turn by 45°.

FIGS. 7A and 7B illustrate in plan view the relations between movingdirection 40 and grooves 3. FIG. 7A shows a raised part 2 turnedcounterclockwise by 45° with respect to moving direction 40. FIG. 7Bshows a raised part 2 turned clockwise by 45° with respect to movingdirection 40. In the method shown in FIG. 7A, the longitudinal directionof the grooves is perpendicular to moving direction 40, while in themethod shown in FIG. 7B the longitudinal direction of the grooves isparallel to moving direction 40.

The selected grooves are the oblique grooves of Test No. <2> out of <1>to <4> in the first printing test. The configuration of the grooves andthe dimension of cross section are identical with those for the parallelgrooves of <2> used in the second printing test in the first embodiment.The results from the second printing test are shown in Table 2 providedabove.

For a turning angle of 0°, balls were produced at a print speed of 1.4m/min. or more, while bubbles or narrownesses were not produced at aspeed of 1.4 m/min. or less. In the first embodiment, the results fromthe turning angle of 0° indicate the occurrence of bubbles ornarrownesses at a print speed of 1.4 m/min., and thus the printing plateof the present embodiment is an improvement over that of the firstembodiment. For a turning angle of 45° counterclockwise (the testingmethod shown in FIG. 7A), neither balls nor bubbles or narrownesses wereproduced at a print speed of 1.4 m/min. or less, while bubbles ornarrownesses were produced at a print speed of 2.0 m/min. A turningangle of 45° clockwise (the testing method shown in FIG. 7B) permittedprinting without balls or bubbles or narrownesses at a print speed of2.0 m/min., as well.

Considering these results together with those in the first embodiment,the oblique grooves are in general superior to the parallel ones in thatit is less likely that balls or the like are produced even with anincreased print speed. Furthermore, for the oblique grooves, printing ispreferably carried out with moving direction 40 being eitherperpendicular or parallel to the grooves, as shown in FIGS. 7A and 7B.The description is not repeated as to other functions and effectssimilar to those for the first embodiment.

When it is to be avoided that a side of the raised part is parallel orperpendicular to the moving direction as shown in the second printingtest, a raised part may be pre-formed in a slanting direction on a mainsurface of the printing plate instead of placing a printing plate ontothe plate cylinder in a slanting direction. In other words, in FIG. 3,each of the sides of nearly-rectangular raised parts 13 a to 13 d isparallel to the corresponding one of the sides of printing plate 1.Alternatively, the raised parts may be provided on printing plate 1 suchthat a side of raised parts 13 a to 13 d and a side of printing plate 1form an angle of 45°, for example, and the printing is conducted inmoving direction 40, which would provide the same effect. For theoblique grooves shown in FIGS. 2A and 2B, a side of the near-rectangleforming an angle of 45° with the moving direction will result in thelongitudinal direction of the grooves being either parallel orperpendicular to the moving direction, thereby allowing rapid printingwith an increased film thickness without producing balls ornarrownesses.

A printing plate or a printing method illustrated in the first andsecond embodiments may be applied in flexography to allow flexographicprinting to produce a film thickness greater than would be achievedusing the conventional art. Further, the invention as described abovemay be applied in an apparatus and method for manufacturing liquidcrystal devices to allow printing a sealing material that may be usedfor bonding panel substrates together for a liquid crystal panel with animproved film thickness on the surface of the panel substrate, therebyproviding improved productivity and quality over the conventional art.

The grooves illustrated in the first and second embodiments have atriangular cross section. As stated above, there may be otherconfigurations such as a trapezoid or a semi-circle. Further, theconfiguration of the cross section of a raised part is not limited to atrapezoid and may be a rectangle, for example. Further, theconfiguration of the raised part, which forms the design for printing,is not limited to a frame and may be linear, or a raised part may coveran entire rectangular region in a planar manner and may not include anempty area within it, as is the case with the frame-shaped raised part.

The above embodiments primarily use a printing substrate and a printingsubstance that can be used for bonding together panel substrates forliquid crystal, although the present invention may be applied to reliefprinting in general and is not limited to a printing apparatus andmethod in conjunction with liquid crystal devices.

As stated above, according to the present invention, relief printingrequiring a film thickness greater than would be achieved using theconventional art may use a printing plate having a raised part withgrooves passing through from one side to another thereof on its printingsurface to allow high precision printing for any forms. When the printedsubstance is to form a nearly-rectangular frame, grooves to be formedmay be the oblique ones and the moving direction may be parallel to thelongitudinal direction of the grooves to prevent balls or the like frombeing produced which would decrease the quality, thereby increasing theprint speed.

The present invention may also be employed in an apparatus and methodfor manufacturing a liquid crystal device to prevent, during thedropping and panel-alignment method, liquid crystal from leaking out orair from being trapped in the seal.

The embodiments disclosed herein are by way of example only and are notby way of limitation. The scope of the present invention is set forth inthe claims rather than the above description, and includes all themodifications within the spirit and scope equivalent to those defined inthe claims.

INDUSTRIAL APPLICABILITY

The present invention is advantageously applicable to flexographyrequiring transfer of a printing substance with increased thickness.Further, it is advantageously applicable to the step of disposing a sealon the surface of the panel substrate during manufacture of a liquidcrystal device.

1. A printing plate comprising a raised part for transferring printingsubstance to a printing substrate, said raised part including, on itsprinting surface, a groove passing through from one side to anotherthereof.
 2. The printing plate according to claim 1, wherein said groovehas a nearly-triangular cross section.
 3. The printing plate accordingto claim 1, wherein a plurality of said grooves extend in one directionand parallel to each other and are equally spaced apart.
 4. The printingplate according to claim 3, being a printing plate for a flexographicpress, wherein said groove has a width along the printing surface ofsaid raised part of not less than 20 μm and not more than 60 μm, a depthnot less than 25 μm and not more than 75 μm, and a distance between thegrooves of not less than 20 μm and not more than 60 μm.
 5. The printingplate according to claim 4, said printing plate including said raisedpart shaped as a nearly-rectangular frame, wherein a side of saidnear-rectangle is parallel to a longitudinal direction of said groove,and said raised part is provided such that said side of saidnear-rectangle is in a slanting direction relative to a moving directionof said printing plate.
 6. The printing plate according to claim 4, saidprinting plate including said raised part shaped as a nearly-rectangularframe, wherein a side of said near-rectangle and a longitudinaldirection of said groove form an angle of approximately 45°.
 7. Theprinting plate according to claim 6, wherein a moving direction of saidprinting plate is substantially perpendicular to the longitudinaldirection of said groove.
 8. The printing plate according to claim 6,wherein the moving direction of said printing plate is substantiallyparallel to the longitudinal direction of said groove.
 9. A presscomprising said printing plate according to claim
 1. 10. An apparatusfor manufacturing a liquid crystal device comprising said printing plateaccording to claim
 1. 11. A method of relief printing comprising: thestep of printing by pressing, on a printing substrate, a printing plateincluding a raised part, said raised part having, on a surface fortransferring printing substances, a plurality of grooves passing throughfrom one side to another thereof, and the step of transferring printingsubstance to the printing substrate by disposing said printing plate ona perimeter surface of a cylindrical plate cylinder and rotating saidplate cylinder.
 12. The printing method according to claim 11, performedby using a flexographic press.
 13. The printing method according toclaim 12, wherein said raised part is shaped as a nearly-rectangularframe, said grooves are linear grooves parallel to each other andequally spaced apart, and the printing substance to be printed onto saidprinting substrate is a sealing material.
 14. The printing methodaccording to claim 13, wherein said sealing material is a sealingmaterial for a flat panel display, said grooves have a width along asurface of said raised parts of not less than 20 μm and not more than 60μm, a depth of not less than 25 μm and not more than 75 μm, and adistance between the grooves of not less than 20 μm and not more than 60μm.
 15. The printing method according to claim 14, wherein said step oftransferring includes the step of rotating said plate cylinder whileusing said printing plate with said grooves being parallel with a sideof said near-rectangle, a moving direction of said printing plateforming an angle of approximately 45° with a longitudinal direction ofsaid grooves.
 16. The printing method according to claim 14, whereinsaid step of transferring includes the step of rotating said platecylinder while using said printing plate with said grooves forming anangle of approximately 45° with a side of said near-rectangle, a movingdirection of said printing plate being substantially perpendicular to alongitudinal direction of said grooves.
 17. The printing methodaccording to claim 14, wherein said step of transferring includes thestep of rotating said plate cylinder while using said printing platewith said grooves forming an angle of approximately 45° with a side ofsaid near-rectangle, a moving direction of said printing plate beingparallel to a longitudinal direction of said grooves.
 18. A method ofmanufacturing a liquid crystal device employing the printing methodaccording to claim 11.